The embodiments of the present invention relate to a semiconductor device and a method of operating the same, more particularly relates to a semiconductor device for storing data and a method of operating the same.
A semiconductor device may include a memory controller and a memory device. A typical non-volatile memory device is a NAND flash memory device that may retain stored information even when the device is not powered.
The recently developed NAND flash memory device uses a multi-level cell MLC method to increase storage capacity of data, one MLC storing two bit data including least significant bit LSB data and most significant bit MSB data. The MSB data is stored after the LSB data is stored in the memory cell. The previously stored LSB data may get lost because of storage error such as an abnormal stop of operation while storing MSB data. For example, threshold voltage of the memory cell remains erase level or is changed to program level according to the stored LSB data. Subsequently, threshold voltage of the memory cell remains at the erase level or is changed to one of first to third program levels according to MSB data, when the MSB data is stored in the memory cell. In the event that a storage error, such as an abnormal stop of storing of the MSB data, occurs during program operation for storing the MSB data, i.e. change of the threshold voltage of the memory cell, the MSB data stored in a register or a page buffer gets lost, and the threshold voltage of the memory cell increases only up to indefinite level different from a target level. As a result, it may be impossible to verify the stored LSB data, which means that the previously stored LSB data may get lost.
In short, the storage error, such as the abnormal stop of storing data during data storage, may cause loss of previously stored data.